The present invention generally relates to methods and apparatus for the parallel deposition, synthesis and screening of an array of diverse materials at known locations on a single substrate surface. The invention may be applied, for example, to prepare covalent network solids, ionic solids and molecular solids. More specifically, the invention may be applied to prepare inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, non-biological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened in parallel for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, and other properties.
The discovery of new materials with novel chemical and physical properties often leads to the development of new and useful technologies. Over forty years ago, for example, the preparation of single crystal semiconductors transformed the electronics industry. Currently, there is a tremendous amount of activity being carried out in the areas of superconductivity, magnetic materials, phosphors, nonlinear optics and high strength materials. Unfortunately, even though the chemistry of extended solids has been extensively explored, few general principles have emerged that allow one to predict with certainty composition, structure and reaction pathways for the synthesis of such solid state compounds. Moreover, it is difficult to predict a prior the physical properties a particular three dimensional structure will possess. Consider, for example, the synthesis of the YBa2Cu3O7-8 superconductor in 1987. Soon after the discovery of the La2xe2x88x92xSrxCuO4 superconductor, which adopts the K2NiF4 structure (Bednorz, J. G. and K. A. Mxc3xcller, Z. Phy. B 64:189 (1986), it was observed that the application of pressure increased the transition temperature (Chu, et al., Phys. Rev. Lett. 58:405 (1987)). As such, Chu, et al. attempted to synthesize a Yxe2x80x94Baxe2x80x94Cuxe2x80x94O compound of the same stoichiometry in the hope that substitution of the smaller element, i.e., yttrium, for lanthanum would have the same effect. Although they found superconductivity above 93K, no phase with K2NiF4 structure was observed (Wu, et al., Phys. Rev. Lett. 58:908 (1987)). Even for the relatively simple intermetallic compounds, such as the binary compounds of nickel and zirconium (Ni5Zr, Ni7Zr2, Ni3Zr, Ni2Zr8, Ni10Zr7, Ni11Zr9, NiZr and NiZr2), it is not yet understood why only certain stoichiometries occur.
Clearly, the preparation of new materials with novel chemical and physical properties is at best happenstance with our current level of understanding. Consequently, the discovery of new materials depends largely on the ability to synthesize and analyze new compounds. Given approximately 100 elements in the periodic table which can be used to make compositions consisting of three, four, five, six or more elements, the universe of possible new compounds remains largely unexplored. As such, there exists a need in the art for a more efficient, economical and systematic approach for the synthesis of novel materials and for the screening of such materials for useful properties.
One of the processes whereby nature produces molecules having novel functions involves the generation of large collections (libraries) of molecules and the systematic screening of those libraries for molecules having a desired property. An example of such a process is the humoral immune system which in a matter of weeks sorts through some 1012 antibody molecules to find one which specifically binds a foreign pathogen (Nisonoff, et al., The Antibody Molecule (Academic Press, New York, 1975)). This notion of generating and screening large libraries of molecules has recently been applied to the drug discovery process. The discovery of new drugs can be likened to the process of finding a key which fits a lock of unknown structure. One solution to the problem is to simply produce and test a large number of different keys in the hope that one will fit the lock.
Using this logic, methods have been developed for the synthesis and screening of large libraries (up to 1014 molecules) of peptides, oligonucleotides and other small molecules. Geysen, et al., for example, have developed a method wherein peptide syntheses are carried out in parallel on several rods or pins (see, J. Immun. Meth. 102:259-274 (1987), incorporated herein by reference for all purposes). Generally, the Geysen, et al. method involves functionalizing the termini of polymeric rods and sequentially immersing the termini in solutions of individual amino acids. In addition to the Geysen, et al. method, techniques have recently been introduced for synthesizing large arrays of different peptides and other polymers on solid surfaces. Pirrung, et al., have developed a technique for generating arrays of peptides and other molecules using, for example, light-directed, spatially-addressable synthesis techniques (see, U.S. Pat. No. 5,143,854 and PCT Publication No. WO 90/15070, incorporated herein by reference for all purposes). In addition, Fodor, et al. have developed, among other things, a method of gathering fluorescence intensity data, various photosensitive protecting groups, masking techniques, and automated techniques for performing light-directed, spatially-addressable synthesis techniques (see, Fodor, et al., PCT Publication No. WO 92/10092, the teachings of which are incorporated herein by reference for all purposes).
Using these various methods, arrays containing thousands or millions of different elements can be formed (see, U.S. patent application Ser. No. 805,727, filed Dec. 6, 1991, the teachings of which are incorporated herein by reference for all purposes). As a result of their relationship to semiconductor fabrication techniques, these methods have come to be referred to as xe2x80x9cVery Large Scale Immobilized Polymer Synthesis,xe2x80x9d or xe2x80x9cVLSIPS(trademark)xe2x80x9d technology. Such techniques have met with substantial success in, for example, screening various ligands such as peptides and oligonucleotides to determine their relative binding affinity to a receptor such as an antibody.
The solid phase synthesis techniques currently being used to prepare such libraries involve the stepwise, i.e., sequential, coupling of building blocks to form the compounds of interest. In the Pirrung, et al. method, for example, polypeptide arrays are synthesized on a substrate by attaching photoremovable groups to the surface of the substrate, exposing selected regions of the substrate to light to activate those regions, attaching an amino acid monomer with a photoremovable group to the activated region, and repeating the steps of activation and attachment until polypeptides of the desired length and sequences are synthesized. These solid phase synthesis techniques, which involve the sequential coupling of building blocks (e.g., amino acids) to form the compounds of interest, cannot readily be used to prepare many inorganic and organic compounds.
From the above, it is seen that a method and apparatus for synthesizing and screening libraries of materials, such as inorganic materials, at known locations on a substrate is desired.
The present invention provides methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is prepared by delivering components of materials to predefined regions on the substrate, and simultaneously reacting the components to form at least two materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared include inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, non-biological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened in parallel for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical and other properties. As such, the present invention provides methods and apparatus for the parallel synthesis and analysis of novel materials having new and useful properties. Any material found to possess a useful property can be subsequently prepared on a large-scale.
In one embodiment of the present invention, a first component of a first material is delivered to a first region on a substrate, and a first component of a second material is delivered to a second region on the same substrate. Thereafter, a second component of the first material is delivered to the first region on the substrate, and a second component of the second material is delivered to the second region on the substrate. The process is optionally repeated, with additional components, to form a vast array of components at predefined, i.e., known, locations on the substrate. Thereafter, the components are simultaneously reacted to form at least two materials. The components can be sequentially or simultaneously delivered to predefined regions on the substrate in any stoichiometry, including a gradient of stoichiometries, using any of a number of different delivery techniques.
In another embodiment of the present invention, a method is provided for forming at least two different arrays of materials by delivering substantially the same reaction components at substantially identical concentrations to reaction regions on both first and second substrates and, thereafter, subjecting the components on the first substrate to a first set of reaction conditions and the components on the second substrate to a second set of reaction conditions. Using this method, the effects of the various reaction parameters can be studied on many materials simultaneously and, in turn, such reaction parameters can be optimized. Reaction parameters which can be varied include, for example, reactant amounts, reactant solvents, reaction temperatures, reaction times, the pressures at which the reactions are carried out, the atmospheres in which the reactions are conducted, the rates at which the reactions are quenched, the order in which the reactants are deposited, etc.
In the delivery systems of the present invention, a small, precisely metered amount of each reactant component is delivered into each reaction region. This may be accomplished using a variety of delivery techniques, either alone or in combination with a variety of masking techniques. For example, thin-film deposition in combination with physical masking or photolithographic techniques can be used to deliver various reactants to selected regions on the substrate. Reactants can be delivered as amorphous films, epitaxial films, or lattice and superlattice structures. Moreover, using such techniques, reactants can be delivered to each site in a uniform distribution, or in a gradient of stoichiometries. Alternatively, the various reactant components can be deposited into the reaction regions of interest from a dispenser in the form of droplets or powder. Suitable dispensers include, for example, micropipettes, mechanisms adapted from inkjet printing technology, or electrophoretic pumps.
Once the components of interest have been delivered to predefined regions on the substrate, they can be reacted using a number of different synthetic routes to form an array of materials. The components can be reacted using, for example, solution based synthesis techniques, photochemical techniques, polymerization techniques, template directed synthesis techniques, epitaxial growth techniques, by the sol-gel process, by thermal, infrared or microwave heating, by calcination, sintering or annealing, by hydrothermal methods, by flux methods, by crystallization through vaporization of solvent, etc. Thereafter, the array can be screened for materials having useful properties.
In another embodiment of the present invention, an array of inorganic materials on a single substrate at predefined regions thereon is provided. Such an array can consists of more than 10, 102, 103, 104, 105 or 106 different inorganic compounds. It should be noted that when gradient libraries are prepared in each of the predefined reaction regions, a virtually infinite number of inorganic materials can be prepared on a single substrate. In some embodiments, the density of regions per unit area will be greater than 0.04 regions/cm2, more preferably greater than 0.1 regions/cm2, even more preferably greater than 1 region/cm2, even more preferably greater than 10 regions/cm2, and still more preferably greater than 100 regions/cm2. In most preferred embodiments, the density of regions per unit area will be greater than 1,000 regions/cm2, more preferably 10,000 regions/cm2, even more preferably greater than 100,000 regions/cm2, and still more preferably 10,000,000 regions/cm2.
In yet another aspect, the present invention provides a material having a useful property prepared by: forming an array of materials on a single substrate; screening the array for a materials having a useful property; and making additional amounts of the material having the useful property. As such, the present invention provides methods and apparatus for the parallel synthesis and analysis of novel materials having new and useful properties.